Why changing the simulation time in thermal simulation, does not change the result that much?

[Saya]

Hello,

I did the simulation of a lead in plane wave exactly like the tutorial "3.3.4 Heating from a standard active implantable medical device", when I change the simulation time in thermal simulation from 3600 s to 36000 s, the max temperature changes from 22.0035 to 22.0049. I would have expected higher value. I'm wondering what's the reason the temperature does not increase that much and is almost the same as before?

Thanks.

[Sylvain]

@Saya said in Why changing the simulation time in thermal simulation, does not change the result that much?:

I'm wondering what's the reason the temperature does not increase that much and is almost the same as before?

The reason is probably simple physics: I imagine the EM field is not depositing a lot of power, so the temperature does not rise very much. In addition, there is a "cooling" effect from the 22C Dirichlet boundary condition. It is a bit like heating a large room with a small candle while the window is open...

Note that you can use the Stationary Thermal solver to compute what the steady state is.

[Saya]

Thanks. The max value of the color scale in the stationary thermal solver is about 10 times higher than transient thermal solver. What should I change in the transient simulation to get the temperature value the same as stationary thermal solver?

[Sylvain]

The steady-state of the temperature equation, if it exists, is the temperature field when time goes to infinity. I don't understand what you are trying to achieve here, but setting the simulation time to a much larger value should give you the same solution as the stationary solver.

[Saya]

Actually the temperature rise is very lower than what is measured in the lab and I'm wondering what is the reason.

I extract the max temperature at a point using a line passing through the point (I find lines of the intersection of the 3 slices xy-xz-yz at max). But the value is much smaller than the value which a point sensor gives and also the max value which the color scale bar shows. What is the reason?